Elevation of cAMP levels of neuroblastoma-hybrid cells for several days increases the activity of voltage-sensitive Ca2+ channels, secretion of acetylcholine at synapses, and the number of synapses formed with striated muscle cells. The acquisition of functional voltage-sensitive Ca2+ channels by hybrid cells is accompanied by an increase in the number of specific binding sites for [3H]-nitrendipine, a Ca2+ channel inhibitor. Putative voltage-sensitive Ca2+ channel proteins were solubilized and purified by affinity column chromatography. Glycoproteins of neuroblastoma-glioma NG108-15 hybrid cells grown in the presence of [35S]-methionine, with or without high cellular cAMP levels, were solubilized and fractionated by lectin column chromatography and by two-dimensional PAGE. Many cAMP dependent changes in glycoproteins were found. These results suggest that cAMP regulates the expression of certain genes and also the post-translational modification of some glycoproteins. Many monoclonal antibodies to neural antigens were generated and characterized. A monoclonal antibody, 14H3, that binds to a membrane protein that is distributed in a dorsal-ventral gradient in retina inhibits synaptogenesis in the inner synaptic layer of retina. Antibody 13H9 recognizes a cell membrane protein that is expressed by all cells in chick retina, but not by neurons or glia in other parts of the nervous system. This protein (180,000 Mr) identifies a compartment of cells that adhere preferentially to one another. Antibody 18B8 binds to antigens in the outer synaptic layer of retina during synaptogenesis that were not detected in adult retina. Antibody 107H11 recognizes an antigen that is expressed only by photoreceptor cells and some cells in the optic tectum. Antibody 113F4 recognizes an antigen in the outer synaptic layer of retina of chick embryos and adults that was not detected in other tissues. Antibodies 16G6 and 93A7 bind to antigens associated with the inner and outer synaptic layers of retina. Antibodies specific for some cell types in retina also were found.